Method for preparing granular weed control products having improved distribution of agriculturally active ingredients coated thereon

ABSTRACT

A method for improving the distribution of agriculturally active ingredients on the surface of granules includes preparing a sprayable liquid solution of at least one agriculturally active ingredient, and applying the sprayable liquid solution on the granules by spraying the liquid solution in atomized form onto the surface of the granules to provide a coating on the surface of the granules which enables substantially all of the agriculturally active ingredient on the granule to be solubilized by the naturally occurring moisture present on the foliage of a treated weed for absorption into the cells of the treated weed when the granules are applied thereto.

This application is a divisional of U.S. patent application Ser. No.11/906,894, filed Oct. 4, 2007 now U.S. Pat. No. 8,288,320, thedisclosures of which is incorporated herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to methods for preparinggranular weed control products and, more particularly, to methods forimproving the distribution of agriculturally active ingredients on suchgranular products.

2. Description of Related Art

Granular weed control products have been known in the consumer lawnindustry which utilize systemic herbicides such as 2,4-D and MCPP-p forfoliar application to broadleaf post-emergent weeds such as dandelionsfor purposes of killing the weeds. The active ingredients used inpreparing these products are generally applied to inert carriers orfertilizer granules as a solid powder or a liquid solution. The level ofactive ingredient (AI) applied to the granular material is generallybased on a specific total weight percentage of the entire productformulation. Normally, the resulting granular materials are then appliedto a treated weed by using a spreader such as a broadcast spreader tospread the granules on the surface of the weed in a manner such that theindividual granules or particles adhere to moist foliage in order tosolublize the active ingredient (AI), thus allowing it to enter the weedcells and kill the plant.

When a homogeneous sample of a typical weed control product is analyzedfor active ingredient (AI) content the overall weight percentageobtainable is the key parameter of focus. However, the distribution ofthe active ingredient (AI) on the surface of the granules is generallynot evaluated or specifically controlled.

As a result of this lack of distribution control, some granules haveactive ingredient (Ai) coatings with thicknesses and/or concentrationsgreater than can be solubilized by available moisture which, in mostcases, comprises morning dew. The literature suggests that a moderatemorning dew, during the spring time can deposit on average 30 mg/cm² ofwater, with a thickness of about 0.3 mm. This factor is generally nottaken into consideration when determining how AI is applied to thefertilizer and inert carrier surface.

However, since weeds transport the available active ingredient (AI) intotheir cell structure on the basis of a concentration gradient, theamount of active ingredient (AI) that can be solubilized will betransported into the weed. To the contrary, if a granular or particulateproduct has a thick coating of active ingredient (AI) and there isinsufficient moisture available to dissolve or solubilize the excessactive ingredient, that excess amount of active ingredient will not betransported into the weed and will be essentially lost for purposes oftreating the plant.

Such active ingredient loss can lead to inconsistent and generally lowerweed control and inefficient utilization of active ingredients. Thus, inview of the problems encountered in controlling the distribution ofactive ingredient on the granular surfaces, many prior weed controlformulations have included significantly greater concentrations ofactive ingredient than would be necessary if processes had beenavailable for controlling the distribution of active ingredient on thegranular surface.

Agricultural formulations can be applied to plants in the form ofsolids, solutions, emulsions, suspensions, dispersions and the like, andare used in agriculture for applying agriculturally active chemicals toplants, soil, insects and the like. Among typical agricultural chemicalsare pesticides such as herbicides, insecticides, fungicides, growthregulators and the like. Other typical agricultural chemicals includeplant nutrients and micronutrients.

In particular, agricultural formulations containing herbicides either assolid powders or liquid solutions can be applied to granular materialand the herbicides coated on the granules to be applied to weed foliageto control the weed plants. Normally, the coated granules are appliedeither in a liquid spray application or in a granular solid applicationto moist weed foliage using a spreader such as a broadcast spreader,with the individual granules desirably adhering to the moist foliage tosolubilize the active herbicidal ingredient, allowing the activeingredient to enter the weed cells and to kill the plant.

Exemplary of relevant prior art in this field is U.S. Pat. No. 5,006,158which discloses that diverse active herbicidal compounds or saltsdisclosed therein can be formulated as granules of relatively largeparticle size, as wettable powders, as emulsifiable concentrates, aspowdery dusts, as flowables, as solutions or as any of several otherknown types of formulations, depending upon the desired mode ofapplication. The formulations containing the actives are disclosed tocontain as little as about 0.5% to as much as about 95% or more byweight of active ingredient. A herbicidally effective amount of theactives is disclosed as depending upon the nature of the seeds or plantsto be controlled and the rate of application varies from about 0.01 toapproximately 10 pounds per acre, preferably from about 0.02 to about 4pounds per acre.

Granular formulations wherein the actives are carried on relativelycoarse particles as disclosed in U.S. Pat. No. 5,006,158 are usuallyapplied without dilution to the area in which suppression of vegetationis desired. Typical carriers for such granular formulations as describedin U.S. Pat. No. 5,006,158 include sand, fuller's earth, attapulgiteclay, bentonite clays, montmorillonite clay, vermiculite, perlite andother organic or inorganic materials which absorb or which may be coatedwith the toxicant. These granular formulations are normally prepared tocontain about 0.1% to about 25% of active ingredients which may includesurface-active agents such as heavy aromatic naphthas, kerosene or otherpetroleum fractions, or vegetable oils; and/or stickers such asdextrins, glue or synthetic resins.

In U.S. Pat. No. 6,890,889, herbicidal formulations comprisingagriculturally active ingredients in combination with an adjuvant systemwere disclosed to optimize post emergent activity on broadleaved weedsin corn. The preferred adjuvant system to optimize weed control andminimize crop response was disclosed to be a crop oil concentrate (COC).Other adjuvant systems for use in the formulation may comprise liquidcompositions such as methylated seed oil (MSO), urea ammonium nitrate(UAN) and ammonium sulfate (AMS). No granular formulations aredisclosed.

In Published U.S. Patent Application US 2005/0096226, herbicidalcompositions useful for controlling weeds in growing crops such as maize(corn) comprising triketone products including mesotrione in combinationwith an organic phosphate, phosphonate or phosphinate adjuvant weredisclosed which can be prepared as a pre-mix concentrate for formulationin various forms including granular formulations with typical carrierssuch as sand, fuller's earth, attapulgite clay, bentonite clays,montmorrilonite clay, vermiculite, perlite and other organic orinorganic materials which absorb or which can be coated with the activecompound.

Thus, when a typical weed control product is analyzed for activeingredient content, the overall weight percentage of active ingredient(AI) obtainable from the product normally is the key parameterconsidered. However, the distribution of the active ingredient on thesurface of the granules has generally not been evaluated or specificallycontrolled and methods for adequately providing such control have notbeen available. This lack of distribution control in the productionprocesses has resulted in significant quantities of granules havingactive ingredient coatings with thicknesses and/or concentrationsgreater than the level that can be solubilized by the availablemoisture, which in most cases is the morning dew. The literaturesuggests that moderate morning dew in the spring in the United Statescan deposit on average 30 mg/cm² of water with a thickness of about 0.3mm.

In foliar treatments, plants transport active ingredients into theircell structure based on a concentration gradient and only the amount ofactive ingredient that can be solubilized will be transported into theweed. Thus, if a granule has a thick coating of active ingredient and ifthere is insufficient moisture on a treated leaf to dissolve theavailable active ingredient present in the coating, the excess activeingredient in the coating will not be transported into the cellstructure of the plant for purposes of enhancing the weed killing effectof the applied granular product.

In this regard, it should be noted that in addition to the economicdisadvantages resulting from waste of active ingredients when excessconcentrations of such active ingredients are applied on the foliarsurface of a weed in order to assure maximum intake of solubilizedactives, governmental restrictions in the U.S. and elsewhere must alsobe taken into consideration concerning the amount of active ingredientthat can be applied for weed control. Such governmental regulations maypreclude the use and/or sale of products which will provide excessiveapplication rates of actives ingredients when applied to weed foliage.

Thus, it has been a continuing problem in the art to provide methods forproduction of granular weed control products having relatively uniformdistribution of active ingredients applied on the granules. In theabsence of such methods, significant economic and functional problemshave been encountered with the granular products produced employingmethods which do not provide adequate distribution control capabilities.Such lack of distribution control can result in products that exhibitinconsistent and generally lower weed control and inefficientutilization of active ingredients including use of significantly greaterconcentrations of the active ingredients to achieve desired levels ofweed control and these quantities may exceed governmental standards.

It would be advantageous to provide methods for producing granularagricultural products having improved control of the distributionpattern of active ingredients on such granular products.

Additionally, it would be advantageous to provide methods for improvingthe distribution of active ingredient (AI) on the surface of a weedcontrol granule enabling reduction of the thickness of the activeingredient coating.

It also would be advantageous to provide methods for minimizing thepotential for AI supersaturation in a granular weed control product andmaximizing transport of the active ingredient (AI) on the granularproduct into the plant cells to cause effective kill of treated weeds.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide methodsfor producing granular agricultural products having improveddistribution of agriculturally active ingredients on the surface of thegranules.

It is another object of this invention to provide methods forcontrolling the thickness of coatings applied on the surface ofagriculturally active granular products to promote the transport of theactive ingredient on the granules into the cells of treated weeds.

Another object of this invention is to provide methods for producingagriculturally active granules having controlled distribution of activeingredients on the granular surface, the granules being adapted forspray application onto foliar surfaces of weeds.

A further object is to provide methods for spraying atomized solutionsof agriculturally active ingredients onto the surface of granules in amanner such that the distribution of the agriculturally activeingredients on the granular surface is controlled to enable enhancedtransport of the active ingredient into the cell structure of a plant,such as a weed, treated with the resulting granular product.

In particular, it is an object of this invention to provide methods forimproving the distribution of agriculturally active ingredients appliedon the surface of granular substrates by spraying liquid solutionscontaining at least one agriculturally active ingredient on granulessuch as fertilizer granules, inert agriculturally acceptable granulesand the like and mixtures thereof through nozzles which atomize at leasta portion of the sprayed liquid solutions enabling the atomized dropletsof the liquid solutions to be deposited on the granular surface at acontrolled deposition rate and, most preferably, in a desired controlleddistribution pattern such as a nonlinear, non-rectangular pattern.

Another particular object of this invention is to provide methods fordispensing a liquid solution containing at least one agriculturallyactive ingredient onto a granular substrate to form an agriculturallyeffective minimum coating thickness on the substrate by spraying theliquid solution through a nozzle onto the granular substrate at acertain deposition rate, preferably about 30-40 grams per second, and ina manner such that at least a portion of the sprayed solution isatomized and a coating is formed on the granular substrate at asufficient thickness to enable substantially all of the agriculturallyactive ingredient on the granular substrate to be solubilized bynaturally occurring moisture when the coated granules are applied toweed foliage such as the leafs of broadleaf weeds.

In this regard, it has been found that by improving the distribution ofthe active ingredient on the surface of the granules and by reducing thethickness of the active ingredient coating, the potential for activeingredient supersaturation is minimized and transport of the activeingredient into the weed cells is maximized.

Accordingly, a higher probability of delivering a lethal dose of activeingredient exists employing weed control products produced in accordancewith the present invention in view of the higher levels of activeingredient transported into treated leaf cell structures whereby agreater percentage of treated weeds, such as broadleaf weeds, are killedat a given active ingredient total formulation concentration on thegranules.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, granular herbicidal productsfor use in controlling weeds in a turfgrass, for example, are providedcomprising agriculturally active ingredients coated on granularsubstrate materials wherein the granular substrates are solid fertilizergranules, inert solid carrier materials and the like and mixturesthereof. In a preferred embodiment, the solid fertilizer granules areorganic or inorganic nitrogen-containing compounds.

Furthermore, in accordance with the present invention, a sprayableliquid solution containing at least one agriculturally active ingredientis prepared and the solution is spray coated, preferably through aparticular nozzle configuration, onto a granular surface such as afertilizer granule, an inert granular substrate and the like andmixtures thereof, at a prescribed deposition rate to provide a desiredcoating thickness and percentage active ingredient coverage of thegranular surface. The sprayable liquid solution may comprise a solutionof the active ingredient in a solvent or may constitute the activeingredient per se in a molten state.

Preferably, the liquid solution is sprayed through nozzles in a mannersuch that at least a portion of the liquid is atomized and the liquid isapplied onto the granular surface in a desired coating thickness and ata desired deposition rate. In this regard, the level of atomization ofthe liquid solution spray is primarily dependent on the droplet sizeand, in a preferred embodiment of this invention, the preferred range ofmean volume droplet diameters (MVD) should be about 100 to about 200microns.

The thickness of the coating of active ingredient applied on the surfaceof the granular substrates herein will depend on a variety of factors.However, it has been found that a minimum effective coating thickness ofactive ingredient to be deposited on the granules to achieve optimalresults when the coated granules are applied on weed foliage should beabout 5.00 micrometers (μm) and the maximum active ingredient coatingthickness should not exceed about 15.00 micrometers (μm) for best weedcontrol results. In preferred embodiments of this invention thethickness of the coating should range from about 2 to about 10micrometers (μm) to produce a granular product which is effective inaccordance with this invention to reduce the potential forsupersaturation and to enable an optimal amount of active ingredient toenter into the leaf cells of a treated plant.

The term “deposition rate” as employed herein refers to the rate atwhich the active ingredient is applied to the surface of the substrategranules and, preferably should be in a range of about 3.7 to about 5.0grams per second of spray solution applied on the granules when thetravel rate of the granules through the spray zone is about 30 to about40 grams per second. The term “spray zone” as employed herein refers tothe area on which atomized liquid from a spray nozzle orifice makescontact with the surface of a granular substrate. The geometry or shapeof the spray zone is determined by the nozzle design (i.e., full cone,hollow cone, flat spray and the like). Most preferably, the ratio ofsolution spray to granule travel rate should range from about 6:1 toabout 8:1 to achieve the most effective deposition rate for activeingredient coating. The travel rate of the granule surface is controlledby the fluidization rate and retention time of the granule processingequipment. The granule processing equipment can be a continuous or batchblender, fluidized bed, and or rotating drum. In this regard, it shouldbe noted that the thickness of the coatings on the granule may becontrolled by the retention time of the granules in the spray zoneand/or the travel rate of the granules through the spray zone at aconstant liquid deposition rate.

Atomization of the liquid spray solution is achieved in accordance withthis invention by spraying the solution of active ingredient throughspray nozzles that have small orifices to create hydraulic pressure thatis significant enough to break apart the fluid stream as it is deliveredto the substrate. It has been found in accordance with this inventionthat nozzles which break apart the solution stream and form a coneshaped spray deposition pattern on the granular substrate are within thepreferred parameters. In this regard, preferred nozzle designs for usein the methods of the present invention are various known nozzle designsincluding hollow cone designs, full cone designs, air assist designs andthe like. However, certain of the known spray nozzle designs such asflat spray nozzles have been found to be ineffective for use herein.

Specifically, full cone design nozzles provide spray patterns on sprayedsubstrate surfaces in the spray zone that may be doughnut shaped, round,square or oval and the spray patterns are completely filled withdroplets. Such nozzles are hydraulically atomized nozzles which containan internal vane or deflector that breaks apart the sprayed solution andimparts controlled turbulence to the liquid prior to a nozzle orifice toform the spray pattern. The spray shape such as the doughnut shaped orcircular spray pattern minimizes over-spray while creating a largeliquid spray area and, thus, increases application coating efficiencyand uniformity. An example of this nozzle design is the UniJet®TG0.4Spray Nozzles, sold by Spraying Systems Co., which develops dropletswith a mean volume droplet diameter (MVD) of 180 microns.

Hollow cone type nozzles which are also hydraulically atomized nozzlesprovide hollow cone spray patterns that are essentially circular ringsof liquid which are generally formed by use of an internal grooved vaneor deflector immediately upstream from a nozzle orifice, or by an inletformed in the nozzle tangential to a whirl chamber. The internaldeflector design or whirling liquid feature of the hollow cone typenozzles helps generate a small liquid droplet size and a relativelylarge spray area. An example of this type of nozzle design is theUniJet® TX2 Spray Nozzles, sold by Spraying Systems Co., which producesdroplets with a mean volume droplet diameter (MVD) of 105 microns.

Another nozzle design useful for spraying agriculturally activeingredients in accordance with this invention is the air assist design.This design uses a high pressure of about 8-12 pounds per square inch(PSI) air stream, which is externally combined with the spray liquidsolution to break apart the stream into fine droplets. The greater thecompressed air flow pressure, the smaller the liquid droplet size for aconstant liquid flow rate. This nozzle design allows an increase in thesolution delivery rate while maintaining small droplet sizes equal tothe hollow cone or full cone designs, by increasing compressed airpressure, thus allowing greater granular travel rates passing throughthe spray zone of about 200-260 grams per second.

Nozzles having characteristics within the above parameters as describedherein atomize the active ingredient liquid into droplets to a size 50%smaller than a flat spray nozzle design. The flat spray nozzle is also ahydraulically atomized liquid design. However, flat spray nozzle designssuch as the VeeJet TP8001 nozzles sold by Spraying Systems Co., which donot include internal deflectors to assist in breaking up the liquid flowhave been found to create a relatively small rectangular pattern on thesurface of the spray zone and to develop a liquid droplet having a meanvolume droplet diameter (MVD) of about 233 microns, have been found tobe ineffective for use in the methods of the present invention.

In this regard, it should be noted that, under similar conditions atpressures of about 100 pounds per square inch (PSI), hollow cone design(TX2) type nozzles develop droplets with a mean volume droplet diameter(MVD) of 105 microns and full cone design (TG0.4) type nozzles developdroplets with a mean volume droplet diameter (MVD) of 180 microns asopposed to the unacceptable flat spray type nozzle designs which developdroplets with a mean volume droplet diameter (MVD) of 233 microns.

Thus, the use of full cone and/or hollow cone and/or air assist nozzlesto spray active ingredients onto granular substrate surfaces in themethods of the present invention for preparing granular weed controlproducts have been found to produce desired active ingredient coating orcoverage areas on such granular substrate surfaces and, also, to providedesired deposition rates for application of such coatings.

Preferred agriculturally active ingredients for use in preparing thesprayable liquid solutions to be used in the methods of this inventionare any pesticidal agents capable of being solubilized and applied inliquid form for treatment of weeds including any one or more of theknown herbicidal compositions. Examples of the wide variety of suitableherbicides for use herein are described in U.S. Pat. Nos. 4,213.776;5,965,487; 5,965,490; 6,022,829; 6,297,197; 6,303,814; 6,417,140;6,579,831; 6,890,889; 6,924,250; 6,962,894 and 7,115,545.

Most preferable herbicides for use in the methods of this invention are2,4-D (2,4-dichloro-phenoxyacetic acid) and MCPP-p(2-(2-methyl-4-chlorophenoxy)propionic acid). As noted, the preferredform of the most preferred herbicides are acidic, and these activeingredients can be dissolved in solvents such as hexylene glycol,aliphatic hydrocarbon mixtures sold by Shell Oil Company under the tradename “ShellSol D-100” or aliphatic hydrocarbon mixtures sold by ExxonChemicals Company under the trade name “Exxsol D110” and methyl esterssuch as biodiesel and the like and mixtures thereof. Preferably sprayingtemperatures ranging from about 70° F. to about 195° F. are employed inaccordance with the present invention.

In a further embodiment of the present invention, the sprayable liquidsolution for use in preparing granular weed control products maycomprise the agriculturally active ingredient per se in a molten state,for example, for use within a spraying temperature range of 200° F.-285°F.

In the methods of the present invention, the granular substrates ontowhich the liquid solutions containing at least one agriculturally activeingredient are sprayed preferably comprise fertilizer granules and maycomprise any type of fertilizer core compound(s). Known chemicalfertilizers including potassium nitrate, potassium sulfate, urea,ammonium nitrate, monopotassium sulfate, ammonium phosphate and the likeand fertilizers obtained from compounding these fertilizer materials maybe employed as the granular substrates in the present invention. Also,fertilizers containing micronutrients or trace elements may be used asthe granules. Examples of suitable UF fertilizers for use herein aredescribed generally in U.S. Pat. No. 6,039,781 for example. Also, otherexamples of fertilizers useful herein are described in U.S. Pat. No.6,579,831.

Further illustrative fertilizers which can be employed as a granularcomposition for use in the present invention include a wide variety offertilizer granules, particles or pellets (which are referred tocollectively herein as fertilizer granules) such as organic andinorganic nitrogen-containing compounds comprising urea,urea-formaldehyde condensation products, amino acids, ammonium salts andnitrates, potassium salts (preferably chlorides, sulfates, nitrates) andphosphoric acid and/or salts of phosphoric acid. Also, it should benoted that the fertilizer granules suitable for inclusion in the presentmixtures may also contain micronutrients, such as iron, manganese,magnesium, boron, copper, zinc and the like.

The physical forms of the fertilizers to be employed in the methods ofthe present invention include granules and extruded particles.Fertilizer granule sizes, preferably, should range from about 1.0 toabout 5.0 mm diameter (most preferably, about 1.5-3.0 mm). Extrudedparticle sizes preferably should range from about 0.6 to about 7.0 mmdiameter (most preferably, about 1.0-3.0 mm). Particle length preferablyshould range from about 0.6 to about 10.0 mm (most preferably, 1.0-5.0mm).

Preferably, the chemical analysis of the fertilizer component to be usedin the present methods should range from about 1 to about 40% by weightelemental nitrogen (N) (most preferably, about 15-36% by weight); about1 to about 30% by weight phosphorous as P₂O₅ (most preferably, about1-27% by weight); and about 1 to about 20% by weight potassium as K₂O(most preferably, about 3-15% by weight). The micronutrient content ofthe fertilizer ingredient, preferably, should range from about 1 toabout 20,000 ppm (parts per million).

In a preferred embodiment of this invention a methyleneurea fertilizeris utilized as the granular substrate for the weed control products sothat when the product is applied to control weeds, for example, in turfapplications, the fertilizer portion of the product will be useful intreating the turf while the selected herbicidally active ingredient willcontrol the weeds.

Examples of inert agriculturally acceptable granular substrates usefulin the methods of the present invention are those described in U.S. Pat.No. 6,579,831. Additionally, suitable inert solid carrier materials foruse herein include any of a variety of organic and/or inorganicmaterials, which may be coated with the agriculturally active ingredientand that have been appropriately ground/fractionated/sized. Suitableorganic materials include agglomerated cellulosic carrier granules suchas Biodac®, sold by Kadant GranTek, Inc., which is described in U.S.Pat. No. 5,843,203. Other suitable organic materials include suchmanufactured, not screened, products having a structure consisting of awood fiber core such as EcoGranules™ sold by Cycle Group, Inc.;compressed coir granular products such those described in U.S. Pat. Nos.6,189,260; 6,408,568 and 6,711,850; corncobs; peanut hulls; processedpaper pulp; sawdust and the like whereas suitable inorganic materialsinclude limestone, diatomaceous earth, gypsum, sand, vermiculite,perlite, fuller's earth and clays such as attapulgite clays, bentoniteclays, montmorillonite clays and mixtures of these substrates.

In preferred embodiments of this invention, methods are provided forapplying a liquid AI solution which, for example, may contain a systemicherbicide such as 2,4-D and MCPP-p on a granular substrate such as amethyleneurea fertilizer, a physical fertilizer blend or an encapsulatedfertilizer or an inert substrate or other substrate. Preferably, theliquid AI solution is sprayed on the granular substrate throughhydraulically atomized spray nozzles having designs such as full cone orhollow cone structures. These full cone or hollow cone nozzle designshave been found to atomize AI solution droplets to a size which mayabout 50% smaller than would be achieved employing a flat spray nozzledesign. In an alternate embodiment, air assist spray nozzles can beutilized and a deposition rate or material travel rate passing throughthe spray zone of 200-260 gm/second is attained. The AI coverage areaemploying any of these application nozzles should equal a sufficientwidth and length to cover the entire surface of the granular substratebeing coated in the spray zone.

Employing the herein described spray nozzle designs, it has been foundthat the AI coating thickness is minimized, reducing the potential forsupersaturation to occur and allowing increased levels of AI to entertreated leaf cells. Preferably, the resulting AI coating thicknessshould range from about 2.0 to about 10.0 micrometers (μm).

The following specific examples are presented to further illustrate andexplain certain aspects of the present invention. However, the Examplesare set forth for illustration only, and are not to be construed aslimiting on the present invention. In the following examples, allpercentages and parts are by weight unless otherwise specified.

In addition, the coating thicknesses described in the following Examplesare based on the percentage of active ingredient coverage generated byspraying liquid active ingredient containing solutions throughparticular nozzle design arrangements. In this regard, it was found thathollow cone nozzle designs provided 46.17% coverage of active ingredienton the sprayed granules while air assist nozzle designs provided 35.31%active ingredient coverage. Based on these findings, the coatingthicknesses were calculated as being 4.88 μm and 6.38 μm, respectively,which thicknesses were within the desired coating thickness ranges forthe desired weed control products. To the contrary, the activeingredient coverage achieved by spraying through flat spray nozzlesresulted in active ingredient coverage of 16.84% providing calculatedcoating thicknesses of 13.37 μm which were significantly greater thanthe desired level of active ingredient coating thicknesses required toavoid the potential for supersaturation when the products are applied toweeds.

Example 1

Four separate sprayable liquid solution samples were prepared bydissolving 70% by weight 2,4-D and 30% MCPP-p active ingredients at atemperature of 265 F. The mixture was heated and agitated for a periodof 20-30 minutes in steam jacketed vessel to ensure uniformity. Using acontinuous Pilot Plant granulation system, an NPK methyleneurea basedfertilizer substrate was prepared at a nutrient analysis of 28-2-3. Theprocess of manufacturing to fertilizer using molten methyleneurea resingenerated a granular fertilizer substrate at a temperature of 85-95 F.The warmed methyleneurea fertilizer was then continuously fed into ablender with retention time such that the material travel rate could bemaintained between 30-40 grams per second through the active ingredientspray zone comprising the total area of the continuous blender whereactive ingredient could be applied to the granular surface. The moltenactive ingredient solution was pumped, on a continuous basis, through asteam jacketed piping system, in order to reach the spray nozzle area ata temperature consistent with the steam jacketed vessel temperature. Thepumping system controlled the rate of active ingredient application suchthat delivery was maintained at 3.7-5.0 grams per second, as well asgenerate a final product analysis with 1.22% 2,4-D and 0.61% MCPP-p tomanufacture four samples of a commercially available Turf Builder® Plus2 (with reduced ‘P’) granular fertilizer (marketed by The Scotts MiracleGro Company, Marysville, Ohio, USA) to produce four coated weed controlproduct samples.

Four different AI spray nozzle designs were employed for spraying theliquid solution onto the granular fertilizer substrate. The first nozzledesign was a flat spray design which displayed a rectangular spraypattern and provided almost no liquid atomization (i.e., MVD of 233microns). The second nozzle design was a full cone (MVD 180 microns)design and the third nozzle design was a hollow cone (MVD 105 microns)design. The full cone and the hollow cone designs displayed circularspray patterns and provided significantly greater liquid atomizationwhen compared to the flat spray design. The fourth nozzle designemployed was an air assist pneumatically operated assembly (pressureorifice) having two fluid zones, one for active ingredient (AI)containing solution and the other for heated compressed air, whichprovided an atomized, fine spray. During each experiment, the liquid AIdeposition rates, as well as the granular substrate material travelrates, were held constant in the targeted ranges of about 3.7 to 5.0grams per second of spray solution applied on the granules at a granuletravel rate of about 30 to about 40 grams per second through the sprayzone.

Once the production of the four weed control product samples wascompleted, a small sample of each was taken and placed into a scanningelectron microscope (SEM) with an energy dispersive spectrometer (EDS)detector. Once the sample was placed in the SEM and testing initiated,the electron beam collided with the sample surface and generatedbackscatter electrons which help form the image of the sample surface.As a result of the collisions, x-rays, having energy levels that arecharacteristic of specific elements and in there respective spatialarrangement on the sample surface, were also generated.

The EDS detector measures the energy from element specific x-raysgenerated during the electron beam scan without losing the element'sspatial arrangement on the sample surface. Quantitative weightpercentages of each element on the surface were estimated by measuringthe total amount of each characteristic X-ray energy generated as theelectron beam collided with the sample. Since 2,4-D and MCPP-p haveelemental chlorine (Cl) in their formula, that element was used todetermine the spatial arrangement of each active ingredient compound onthe granule surface. Using this technique on samples that were nottreated with active ingredient, it was determined that the surface ofthe methyleneurea fertilizer granules were almost completely coveredwith elemental nitrogen (N), oxygen (O), and carbon (N). Based on thatfinding, the percentage of the surface covered with active ingredientwas estimated by first measuring the total quantitative weight ofnitrogen (N) detected and then measuring the quantitative weight ofchlorine (Cl), without altering their spatial arrangement on the samplesurface. The ratio of the chlorine wt % and the nitrogen wt % were usedto estimate the percentage of active (AI) coverage on the particles.

This procedure was replicated three times for each sample evaluated anda summary of the results achieved by application of the liquid solutionson the granular fertilizer substrates as described herein including theweight percents of elemental nitrogen and chlorine, the ratio ofelemental chlorine to elemental nitrogen and the coating thicknessescalculated from elemental maps is shown in the following table for eachnozzle design.

Air Assisted Flat Spray Full Cone Hollow Cone Spray Nozzles SprayNozzles Spray Nozzles Nozzles (Controls) Wt % N 35.29 30.16 34.09 37.51Wt % Cl 7.93 13.71 11.93 6.29 Cl:N Ratio 0.2267 0.4617 0.3531 0.1684Thickness of 9.93 4.88 6.38 13.37 Coating, μm

The tabulated results demonstrate that a coating thickness in the rangeof about 2-10 μm was achieved by spraying atomized droplets of theliquid solution onto the substrates using the full cone, the hollow coneand the air assisted nozzle designs. With the testing indicating thatthe air assist and the hollow cone designs provided the best overallactive ingredient distribution on the granular substrate surfaces.

To the contrary, the flat spray nozzles (designated as Controls) whichcaused rectangular spray patterns without atomization of the sprayeddroplets, resulted in coatings of 13.37 μm which were significantlygreater than the desired coating thickness range so that these samplescould result in active ingredient (AI) supersaturation when the productis applied for weed control which would cause active ingredient (AI)waste.

Example 2

Coated fertilizer granules prepared in accordance with the procedures ofExample 1 by spraying of the liquid solutions on the fertilizer granulesdescribed therein using the indicated spray nozzle designs, were spreadby using a laboratory spreader device, onto dandelion and white coverweeds in early morning and with naturally occurring dew in MarysvilleOhio. The test began in mid-September and the percentage weed controlachieved four weeks after application was noted and tabulated asfollows:

Percentage Weed Control Achieved By Spray Application of Coated Granules(% Control) Flat Spray Full Cone Hollow Cone Hollow Cone Nozzles SpraySpray Spray (Controls) Nozzles Nozzles Nozzles Dan- Dan- White Dan-White Dan- White de- White delion Clover delion Clover delion Cloverlion Clover 78.3 69.4 90.8 74.6 91.7 60.4 66.1 39.5

As demonstrated by the percentage weed control results shown in thetable, coated granular products having the active ingredient (AI)incorporated in the liquid solution sprayed onto the Turf Builder® Plus2 (with reduced ‘P’) granular fertilizer surface through the flat sprayControl nozzles which provided a rectangular spray pattern withoutatomization when applied to the indicated plants in the early morning inMarysville Ohio and having naturally occurring dew thereon, resulted inonly 66.1% control of dandelion plants and 39.5% control of white cloverplants, whereas products produced by spraying atomized droplets of theliquid solution onto the fertilizer granules using the full cone, andthe hollow cone designs resulted in 78.3% to 91.7% control of dandelionplants and 69.4% to 74.6% control of white clover plants.

This significant improvement in weed control demonstrated in thisexample was unexpected and attributable to the combination of thesprayable liquid solution employed and the atomizing effect of thenozzles through which the liquid solutions were applied to the granules,particularly, when the generally circular spray pattern demonstratedwhen full cone and hollow cone nozzles were employed.

Although the invention has been described in its preferred forms with acertain degree of particularity, it is to be understood that the presentdisclosure has been made by way of example only. Numerous changes in thedetails of the compositions and ingredients therein as well as themethods of preparation and use will be apparent without departing fromthe spirit and scope of the invention, as defined in the appendedclaims.

What is claimed is:
 1. A method for preparing granular weed controlproducts comprising: spraying atomized droplets of a liquid solutioncomprising at least one agriculturally active ingredient onto thesurface of granules to provide a coating on the surface of the granules,wherein the coating has a thickness in a range of about 2.00 μm to about10.00 μm, and wherein the agriculturally active ingredient is2-(2-methyl-4-chlorophenoxy)propionic acid, 2,4-dichlorophenoxyaceticacid, or a mixture thereof.
 2. The method of claim 1, wherein theatomized droplets of the liquid solution are sprayed through at leastone full cone or hollow cone nozzle at a deposition rate in a range ofabout 3.7 to about 5.0 grams per second of spray solution applied on thegranules at a travel rate of the granules through a spray zone is about30-40 grams per second.
 3. The method of claim 2, wherein the ratio ofgranule travel rate to solution spray ranges from about 6:1 to about8:1.
 4. The method of claim 1, wherein the atomized droplets of theliquid solution are sprayed through at least one air assisted spraynozzle to provide hydraulically atomized droplets at a deposition rateof about 200-260 grams per second.
 5. The method of claim 1, wherein thegranules are fertilizer granules, inert agriculturally acceptablegranular substrates, or mixtures thereof.
 6. The method of claim 1,wherein the liquid solution comprises2-(2-methyl-4-chlorophenoxy)propionic acid, 2,4-dichlorophenoxyaceticacid, or a mixture thereof, in a solvent.
 7. The method of claim 6,wherein the granules are fertilizer granules, ftftel inertagriculturally acceptable granular substrates, or mixtures thereof. 8.The method of claim 7, wherein the inert agriculturally acceptablegranular substrate is agglomerated cellulosic carrier granules, woodfiber core granules, compressed coir granules, corncobs, peanut hulls,processed paper pulp, sawdust, limestone, diatomaceous earth, gypsum,sand, vermiculite, perlite, Fuller's earth, clay, or mixtures thereof.9. The method of claim 1, wherein the liquid solution is applied on thesurface of the granule through at least one atomizing spray nozzle. 10.A method for dispensing a liquid solution comprising at least oneagriculturally active ingredient onto a granular substrate comprisingspraying the liquid solution through at least one atomizing spray nozzleonto the granular substrate to form a coating on the granular substrate,wherein the coating has a thickness in a range from about 2.00 μm toabout 10.00 μm, and wherein the agriculturally active ingredient is anherbicide that is in a molten state within the temperature range of200-285° F.
 11. The method of claim 10, wherein the atomizing spraynozzle comprises an air assisted spray nozzle providing hydraulicallyatomized droplets of the liquid solution at a deposition rate of about200-260 grams per second.
 12. The method of claim 10, wherein atomizingspray nozzle is a full cone or hollow cone nozzle having a plurality oforifices generally arranged to provide a desired pattern when a liquidsolution is dispensed from the nozzles at a deposition rate in a rangeof about 3.7 to about 5.0 grams per second of spray solution on granulestraveling through a spray zone at a travel rate of about 30-40 grams persecond.
 13. The method of claim 10, wherein the nozzle is a full conedesign nozzle.
 14. The method of claim 10, wherein the nozzle is ahollow cone design nozzle.
 15. The method of claim 10, wherein thenozzle is an air assist design nozzle.
 16. The method of claim 1,wherein the liquid solution does not comprise a solvent.
 17. The methodof claim 10, wherein the liquid solution does not comprise a solvent.18. The method of claim 10, wherein the agriculturally active ingredientis 2,4-dichlorophenoxyacetic acid.
 19. The method of claim 10, whereinthe agriculturally active ingredient is2-(2-methyl-4-chlorophenoxy)propionic acid.
 20. A method for preparinggranular weed control products comprising spraying atomized droplets ofa liquid solution comprising at least one agriculturally activeingredient dissolved in a solvent onto the surface of the granules toform a coating on the surface of the granules, wherein theagriculturally active ingredient is an herbicide, wherein the coatinghas a thickness in a range of about 2.00 μm to about 10.00 μm, andwherein the liquid solution is sprayed at a temperature range of 70-195°F.
 21. The method of claim 20, wherein the agriculturally activeingredient is 2,4-dichlorophenoxyacetic acid.
 22. The method of claim20, wherein the agriculturally active ingredient is2-(2-methyl-4-chlorophenoxy)propionic acid.
 23. The method of claim 1,wherein the agriculturally active ingredient is2,4-dichlorophenoxyacetic acid.
 24. The method of claim 1, wherein theagriculturally active ingredient is2-(2-methyl-4-chlorophenoxy)propionic acid.
 25. The method of claim 20,wherein the liquid solution is coated at a deposition rate of 200-260grams per second.